Almost two million long-haul trucks deliver various goods throughout the United States each year. The great majority of long haul trucks utilize some form of diesel engine. It is not uncommon for long-haul trucks to be driven 150,000 miles annually.
During trips as well as during loading and unloading operations truck engines are operated at idle for an average of 1900 hours. Idling large diesel engines is necessary to provide power needed to operate the truck equipment, power lights, appliances, communication gear, and air conditioning or heating for the cab and sleeping area when drivers are resting. Idling the engines for heavy trucks can cost about $1.25/hr in fuel, $0.07/hr in preventative maintenance, and $0.07/hr in overhaul costs at current fuel and maintenance rates.
While idling an engine provides the power needed to maintain a comfortable environment for the driver it has unwanted consequences. Operating a high horsepower diesel engine at low RPM under light load results in the incomplete combustion of fuel and gives off undesirable exhaust emissions. In addition, operating the diesel engine at low speed causes twice the wear of internal parts compared with the road speed RPM.
Auxiliary power units (APU's) are known which provide power while significantly reducing the need to idle the primary engine. The incentives for using APU's include reduced fuel use and engine wear, prolonged engine life and cuts in maintenance costs, and elimination of approximately 70%–90% of diesel emissions during long periods of engine idling.
Auxiliary power units are portable, truck mounted systems that can provide climate control and power for trucks without the need to operate the primary diesel engine at idle. Prior art systems generally consist of a small internal combustion engine (usually diesel) equipped with a variety of accessories.
The APU diesel engine uses the same coolant and coolant system as the primary diesel engine. During stops when the primary diesel is turned off the APU diesel circulates the coolant to the primary diesel to keep it warm during winter months for easy starts. The same coolant is also routed to the heater core inside the cabin to provide heat to the drive. The APU alternator can provide power for the interior lights, marker lights, and recharging the battery. An inverter can convert the alternator DC current to 110V AC power for televisions and microwaves. The APU air conditioner compressor uses the primary engine installed refrigerant, expansion valve, evaporator, and blower to provide chilled and dehumidified air to the cabin. The APU has its own condenser to reject the heat from the refrigerant.
As an example, APU's are known which comprise a two cylinder diesel engine driving a generator and an alternator. The generator provides power to a 110 v HVAC system (separate from the factory installed air conditioning system) and electrical receptacles for microwaves, TVs, etc. The alternator is used to charge the batteries and run marker lights. In some instances, the small diesel engine drives a water pump that circulates coolant to the large diesel engine to keep it warm for starting during the winter months.
Another known APU comprises a small diesel engine which drives a generator. The generator provides power for electrically driven accessories such as the air conditioning compressor and the water pump. Since the accessories are driven by electrical motors and are powered by the APU, the primary diesel engine can be off. The speed of each accessory can be individually controlled and, therefore, provide only the conditioned air or such other power needed at that moment. The accessories are not forced to rotate at some fixed speed ratio of the engine speed.
Representative of the art is U.S. Pat. No. 6,048,288 (2000) to Tsujii et al. which discloses an engine wherein auxiliary machines are operated by a motor generator where the engine is stopped to reduce electric power consumption.
What is needed is an auxiliary power system for a motor vehicle engine using a secondary engine to drive the motor vehicle engine belt driven accessories through a hydraulic system and one-way clutches when the motor vehicle primary engine is turned off. The present invention meets this need.